1. Field of the Invention
The present invention relates to a scroll compressor, and in particular to a structure of a driving pin for a scroll compressor which is capable of transmitting a rotational force by being combined with a rotating scroll.
2. Description of the Background Art
Generally, a compressor is for compressing a compressible fluid by using mechanical energy and can be divided into a reciprocating type, a scroll type, centrifugal type and a vane type, etc.
Unlike a reciprocating type compressor using a linear motion of a piston, a scroll type compressor (hereinafter, it is referred to as a scroll compressor) sucks, compresses and discharges gas by using a rotational body similar to a centrifugal type compressor and a vane type compressor.
FIG. 1 is a longitudinal sectional view illustrating the conventional scroll compressor.
As depicted in FIG. 1, the conventional scroll compressor includes a casing 1 filled with oil up to a certain height, a main frame 2 and a sub frame 3 respectively fixed to the upper and the lower portions of the inner circumference of the casing 1, a driving motor 4 installed between the main frame 2 and the sub frame 3 and having a stator 4A and a rotor 4B, a rotational axis 5 placed so as to fit for the center of the rotor 4B of the driving motor 4 and penetrating through the main frame 2, a rotating scroll 6 combined with the rotational axis 5 and installed to the upper surface of the main frame 2, a fixed scroll 7 fixed to the upper surface of the main frame 2 so as to form a plurality of compressing chambers by being coupled to the rotating scroll 6, a high/low pressure division plate 8 installed to the upper portion of the fixed scroll 7 and dividing the inner space of the casing 1 into a suction pressure region and a discharge pressure region, and a counterflow prevention valve assembly 9 combined with the upper surface of the high/low pressure division plate 8 and preventing a counterflow of discharged gas.
FIG. 2 is a longitudinal sectional view illustrating a shape and an assembly state of a slide bush and a driving pin of the conventional scroll compressor.
As depicted in FIG. 2, in the rotational axis 5, a driving pin 5a eccentrically projects from the upper end of the rotational axis 5 in order to rotate the rotating scroll 6, and a slide bush 10 inserted into the boss 6b of the rotating scroll 6 is slides over the driving pin 5a inserted therein.
In addition, a sliding hole 10a having a guide surface (not shown) is formed at the inner circumference of the slide bush 10. The sliding hole 10a is a relatively deep hole in order to permit a sliding-contact between a sliding surface (not shown) of the driving pin 5a and the sliding hole 10a. 
In FIGS. 1 and 2, reference numeral 6a is a wrap of the rotating scroll 6, reference numeral 7a is a wrap of the fixed scroll 7, and reference numeral DP is a discharge pipe.
The operation of the conventional scroll compressor will be described hereinafter.
When power is applied, the rotor 4B rotates beside the stator 4A together with the rotational axis 5, and the driving pin 5a formed at the upper portion of the rotational axis 5 eccentrically rotates together. The rotating scroll 6 connected to the driving pin 5a rotates by the eccentric rotation of the driving pin 5a over an eccentric distance. A body capacity of the plurality of compressing chambers formed by the wraps 6a, 7a of the rotating scroll 6 and the fixed scroll 7 is decreased while being moved to the center portion by the continuous rotational motion of the rotating scroll 6 Accordingly, refrigerant gas is sucked, compressed and discharged by the compressor.
FIG. 3 is a perspective view illustrating a load distribution of the driving pin of the conventional scroll compressor.
However, in the conventional scroll compressor, the rotational force of the driving motor 4 is transmitted to the rotating scroll 6 by the driving pin 5a engaging the slide bush 10. As depicted in FIG. 3, because the side surface of the driving pin 5a contacting the slide bush 10 receives a reactive force, a bending moment M1 according to this contact acts on the driving pin 5a. Particularly, by the force and the moment acting on the side surface of the driving pin 5a, a stress acts on each surface of the driving pin 5a. The stress is especially concentrated on the start portion of the driving pin 5a, accordingly the driving pin 5a may be damaged due to the stress concentration when the scroll compressor is used for a long time.
In order to solve the above-mentioned problem, it is an object of the present invention to provide a driving pin structure for a scroll compressor which is capable of preventing a damage of a driving pin due to a stress concentration from happening by reducing a bending moment acted on the driving pin of a rotational axis.
In order to achieve the object of the present invention, in a scroll compressor comprising a fixed scroll having a wrap, a rotating scroll having a wrap engaged with the wrap of the fixed scroll and performing a rotational motion in a radial direction of the rotational axis of a driving device, a driving pin eccentrically formed at the rotational axis of the driving device and inserted into a boss of the rotating scroll and a bush member interposed between the boss of the rotating scroll and the driving pin, the driving pin has a length shorter than a length of the bush member.